The present invention relates to a method for fabricating a resin-encapsulated semiconductor device using a surface-mounted lead frame in which leads are exposed on the bottom surface of a resin-encapsulated portion (package).
In recent years, there is an increasing demand for high-density mounting of semiconductor elements on electronic devices in order to realize smaller electronic devices with higher functionalities. Accordingly, the overall size and the thickness of a semiconductor element such as a resin-encapsulated semiconductor device (a device obtained by integrally encapsulating a semiconductor chip and leads in an encapsulation resin) have been quickly reduced. Therefore, various techniques have been developed for the fabrication of semiconductor elements such as resin-encapsulated semiconductor devices in order to reduce the production cost and to increase the productivity. For example, a molding method has been developed in the art, in which a plurality of semiconductor chips are individually encapsulated in an encapsulation resin after the die bonding step and the wire bonding step. A process of resin encapsulation according to a conventional molding method will now be described with reference to FIG. 7A to FIG. 7C, FIG. 8A and FIG. 8B.
FIG. 7A to FIG. 7C are perspective views schematically illustrating a resin encapsulation apparatus used in a conventional molding method and a process of resin encapsulation with such an apparatus. FIG. 8A and FIG. 8B are cross-sectional views illustrating the inside of an encapsulation mold set during the resin encapsulation process.
As illustrated in FIG. 7A, the resin encapsulation apparatus is capable of holding an encapsulation tape 1015 under a constant tension.
As illustrated in FIG. 7B, a lead frame 1000 carrying a number of semiconductor chips thereon is set on a lower mold 1052, and resin tablets 1062 are placed in encapsulation resin supply sections 1061 of the lower mold 1052.
Then, as illustrated in FIG. 8A, the lead frame 1000 is clamped between an upper mold 1051 and the lower mold 1052. At this time, a melted encapsulation resin is supplied by a plunger 1058 from below into semiconductor product molding sections 1060, whereby a resin-encapsulated semiconductor device 1055 is injection-molded in each die cavity. Upon completing the injection molding and opening the lower mold 1052, the encapsulation tape 1015 is separated from a resin cull 1063 and the resin-encapsulated semiconductor device 1055 illustrated in FIG. 7C.
However, in the conventional molding method, when the lead frame 1000 is clamped between the upper mold 1051 and the lower mold 1052, a gas (e.g., an air left therein due to warping of the lead frame 1000, etc., a vapor generated from the encapsulation tape 1015 due to a temperature increase, or an organic material gas) may be entrapped in the slight gap between the encapsulation tape 1015 and the opposing upper mold 1051. If the lead frame 1000 is clamped between the upper mold 1051 and the lower mold 1052 with such a gas being entrapped, the gas will not be discharged out of the gap between the upper and lower molds. Moreover, subsequent injection of an encapsulation resin into the cavity may push the entrapped gas away from a resin injection gate 1070, as illustrated in FIG. 8B, thereby deforming the lead frame 1000 by the pressure of the gas being pushed. An excessive deformation of the lead frame 1000 may cause a semiconductor chip 1021 and/or a thin metal wire 1022 to come into contact with the lower mold 1052, thereby damaging or deforming the semiconductor chip 1021 and/or the thin metal wire 1022.
The present invention has been made in order to solve this problem in the prior art, and has an object to suppress the deformation of a lead frame during the resin encapsulation step.
A lead frame of the present invention is a lead frame used in resin encapsulation of a semiconductor chip using an encapsulation mold that includes a die cavity to be filled with an encapsulation resin, the lead frame including: a first region exposed to the die cavity; a second region that is surrounding the first region and to be clamped by the encapsulation mold; a third region exposed to an ambient air with the die cavity being filled with the encapsulation resin; and at least one groove formed on a surface of the lead frame that is opposite to another surface of the lead frame on which the first region is present, the at least one groove extending from an area corresponding to the first region across another area corresponding to the second region so as to reach the third region.
When a resin-encapsulated semiconductor device is fabricated with a resin creepage preventing member being attached to one surface of the lead frame of the present invention that is opposite to the surface thereof on which the first region is present, the air entrapped between the resin creepage preventing member and the encapsulation mold is pushed into the second region clamped by the encapsulation mold due to the pressure from the resin being injected into the die cavity in the resin encapsulation process. The air being pushed lifts the resin creepage preventing member covering at least one groove toward the lead frame, i.e., into the at least one groove. The at least one groove extends from an area corresponding to the first region across another area corresponding to the second region so as to reach the third region that is exposed to the ambient air, whereby the air lifting the resin creepage preventing member into the at least one groove is discharged to the outside of the encapsulation mold. Therefore, in the fabrication of a resin-encapsulated semiconductor device, it is possible to suppress/prevent the lead frame from being deformed, and to suppress/prevent a damage to semiconductor chips, a deformation and disruption of thin metal wires, etc., which may otherwise occur due to the deformation of the lead frame.
The at least one groove may be a U-shaped groove; and the third region may be a side edge of the lead frame surrounding the second region.
The at least one groove may be a U-shaped groove that includes a through hole connecting the at least one groove to the third region.
A method for fabricating a resin-encapsulated semiconductor device of the present invention includes the steps of: (a) preparing a lead frame, including: a first region; a second region surrounding the first region; a third region located outside the second region; and at least one groove formed on a surface of the lead frame that is opposite to another surface of the lead frame on which the first region is present, the at least one groove extending from an area corresponding to the first region across another area corresponding to the second region so as to reach the third region; (b) providing a resin creepage preventing member on the area corresponding to the first region; (c) mounting a semiconductor chip on the first region of the lead frame; and (d) clamping the second region by an encapsulation mold that includes a die cavity so as to place the semiconductor chip into the die cavity, and filling the die cavity with a resin.
With this fabrication method, in the resin filling step, the air entrapped between the resin creepage preventing member and the encapsulation mold is pushed into the second region clamped by the encapsulation mold due to the pressure from the resin being injected into the die cavity. The air being pushed lifts the resin creepage preventing member covering at least one groove toward the lead frame, i.e., into the at least one groove. The at least one groove extends from an area corresponding to the first region across another area corresponding to the second region so as to reach the third region that is located outside the second region and is not clamped by the encapsulation mold, whereby the air lifting the resin creepage preventing member into the at least one groove is discharged to the outside of the encapsulation mold. Therefore, in the fabrication of a resin-encapsulated semiconductor device, it is possible to suppress/prevent the lead frame from being deformed, and to suppress/prevent a damage to semiconductor chips, a deformation and disruption of thin metal wires, etc., which may otherwise occur due to the deformation of the lead frame.
In the step (a), the at least one groove may be a U-shaped groove; and the third region may be a side edge surrounding the second region.
In the step (a), the at least one groove may be a U-shaped groove that includes a through hole connecting the at least one groove to the third region.
In the step (b), the resin creepage preventing member is preferably provided along a surface of the at least one groove.
In this way, the air that has been pushed into the second region clamped by the encapsulation mold in the resin encapsulation process is discharged to the outside of the encapsulation mold, whereby the pressure for lifting the resin creepage preventing member covering the at least one groove toward the lead frame, i.e., into the at least one groove, is not required. Therefore, the air discharging efficiency is improved.
Another method for fabricating a resin-encapsulated semiconductor device of the present invention includes the steps of: (a) preparing a lead frame including a first region and a second region surrounding the first region; (b) providing a resin creepage preventing member on an area corresponding to the first region and another area corresponding to the second region, the resin creepage preventing member including at least one U-shaped groove extending from a position corresponding to the first region across the area corresponding to the second region so as to reach a side edge surrounding the second region; (c) mounting a semiconductor chip on the first region of the lead frame; and (d) clamping the second region by an encapsulation mold that includes a die cavity so as to place the semiconductor chip into the die cavity, and filling the die cavity with a resin.
With this fabrication method, in the resin filling step, the air entrapped between the resin creepage preventing member and the encapsulation mold is pushed into the second region clamped by the encapsulation mold due to the pressure from the resin being injected into the die cavity. The air being pushed is discharged to the outside of the encapsulation mold through at least one groove that is provided in the resin creepage preventing member and extends from an area corresponding to the first region across another area corresponding to the second region so as to reach a side edge that is surrounding the second region and is not clamped by the encapsulation mold. Therefore, in the fabrication of a resin-encapsulated semiconductor device, it is possible to suppress/prevent the lead frame from being deformed, and to suppress/prevent a damage to semiconductor chips, a deformation and disruption of thin metal wires, etc., which may otherwise occur due to the deformation of the lead frame.
Still another method for fabricating a resin-encapsulated semiconductor device of the present invention includes the steps of: (a) preparing a lead frame including a first region and a second region surrounding the first region; (b) providing a resin creepage preventing member on an area corresponding to the first region and another area corresponding to the second region, the resin creepage preventing member including a satin finished surface on the area corresponding to the first region and the area corresponding to the second region; (c) mounting a semiconductor chip on the first region; and (d) clamping the second region by an encapsulation mold that includes a die cavity so as to place the semiconductor chip into the die cavity, and filling the die cavity with a resin.
With this fabrication method, in the resin filling step, the air entrapped between the resin creepage preventing member and the encapsulation mold is moved by the pressure from the resin being injected into the die cavity through spaces between the minute surface irregularities of the satin finished surface of the resin creepage preventing member, and is discharged to the outside of the encapsulation mold before the lead frame is deformed. Therefore, in the fabrication of a resin-encapsulated semiconductor device, it is possible to suppress/prevent the lead frame from being deformed, and to suppress/prevent a damage to semiconductor chips, a deformation and disruption of thin metal wires, etc., which may otherwise occur due to the deformation of the lead frame.
Still another method for fabricating a resin-encapsulated semiconductor device of the present invention includes the steps of: (a) preparing a first encapsulation mold including a die cavity and a clamp section and a second encapsulation mold including a surface corresponding to the die cavity and another surface corresponding to the clamp section, the second encapsulation mold including at least one groove extending from an area corresponding to the die cavity across another area corresponding to the clamp section so as to reach still another area surrounding the area corresponding to the clamp section; (b) preparing a lead frame including a first region and a second region surrounding the first region; (c) providing a resin creepage preventing member on an area corresponding to the first region and another area corresponding to the second region; (d) mounting a semiconductor chip on the first region of the lead frame; and (e) clamping the second region by the first encapsulation mold and the second encapsulation mold so as to place the semiconductor chip into the die cavity, and filling the die cavity with a resin.
With this fabrication method, in the resin filling step, the air entrapped between the resin creepage preventing member and the second encapsulation mold is discharged to the outside of the encapsulation mold, before the lead frame is deformed, through at least one groove that is provided in the second encapsulation mold and extends from an area corresponding to the die cavity across another area corresponding to the clamp section so as to reach still another area surrounding the area corresponding to the clamp section. Therefore, in the fabrication of a resin-encapsulated semiconductor device, it is possible to suppress/prevent the lead frame from being deformed, and to suppress/prevent a damage to semiconductor chips, a deformation and disruption of thin metal wires, etc., which may otherwise occur due to the deformation of the lead frame.
Still another method for fabricating a resin-encapsulated semiconductor device of the present invention includes the steps of: preparing a first encapsulation mold including a die cavity and a clamp section and a second encapsulation mold including a surface corresponding to the die cavity and another surface corresponding to the clamp section, the surface corresponding to the die cavity and the surface corresponding to the clamp section being satin finished; (b) preparing a lead frame including a first region and a second region surrounding the first region; (c) providing a resin creepage preventing member on an area corresponding to the first region and another area corresponding to the second region; (d) mounting a semiconductor chip on the first region of the lead frame; and (e) clamping the second region by the first encapsulation mold and the second encapsulation mold so as to place the semiconductor chip into the die cavity, and filling the die cavity with a resin.
With this fabrication method, in the resin filling step, the air entrapped between the resin creepage preventing member and the encapsulation mold is moved by the pressure from the resin being injected into the die cavity through spaces between the minute surface irregularities of the satin finished surface of the second encapsulation mold, and is discharged to the outside of the encapsulation mold before the lead frame is deformed. Therefore, in the fabrication of a resin-encapsulated semiconductor device, it is possible to suppress/prevent the lead frame from being deformed, and to suppress/prevent a damage to semiconductor chips, a deformation and disruption of thin metal wires, etc., which may otherwise occur due to the deformation of the lead frame.